Abstarct: Shear strength of rock masses, joints and discontinuities are important in analysis of the stability of rock slopes and other structures designed and executed in rock. Shear strength of rock mass is mainly controlled by weakness planes. Therefore, it is vital to understand factors affecting shear strength of rock masses. Shear strength parameters of rock are determined in a variety of methods. Direct shear test performed in field or laboratory on natural samples is one of these methods. Sometimes, direct shear test of rocks performs on natural joints of rock, and sometimes on the gaps in rock. In this research, analysis of shear strength of contact joint between concrete and rock has been done by using two-dimensional modeling in PFC2D discrete element method. Models include three different level of 1.5, 3 and 6 MPa of normal vertical stress. Results of numerical modeling are compared with the results of laboratory and field tests. According to results from direct shear test and JRC analysis before and after shearing, it was determined that shear strength of joints increases by increasing roughness. Also by increasing normal stress on low roughness joint surfaces, the distance between final shear strength and residual shear strength is less than high roughness joint surfaces.